應用鱸鰻（Anguilla marmorata）及亞洲蜆（Corbicula fluminea）作為生物指標組合評估河川的金屬污染衝擊

Abstract

由人口增加、工業及經濟發展所導致之金屬污染已嚴重危害許多都市型河川。以具代表性之指標生物進行生物監測，已被廣泛使用於評估金屬污染對河川之衝擊。此方法可獲知一定時間範圍內，生物受環境中金屬污染的結果，因而對污染造成河川生態系之衝擊有全面性的認知。本研究使用鱸鰻(Anguilla marmorata)及亞洲蜆(Corbicula fluminea)作為生物指標組合，應用於台灣北部一典型都市型河川─大屯溪，以反映其金屬污染之情形。儘管環保署於大屯溪未受污染之上游河段具季節性水質監測，於下游沿岸土地利用以工業及住宅為主之都市化河段，卻未施行環境監測或生物監測。 研究中使用現地捕捉之鱸鰻及移殖24天之亞洲蜆，分析其不同部位之金屬(砷、鎘、鉻、銅、錳、鎳、鉛、鋅)濃度，並與河川水體中之金屬濃度進行比較，其濃度取自環保署監測資料及本研究於下游地區之量測結果。 研究結果顯示，相較上游環保署監測樣點，金屬污染物集中於大屯溪之下游地區。各項金屬皆累積於鱸鰻體內，其中砷、鎘、銅、錳及鋅於不同部位間的累積濃度具顯著差異(Kruskal-Wallis test, p<0.05)，主要累積於腸(砷：1.20 μg g-1 DW、鋅：154 μg g-1 DW)、肝(鎘：0.66 μg g-1 DW、銅：31.9 μg g-1 DW)及脊椎(錳：31.1 μg g-1 DW)組織。亞洲蜆移殖實驗結果顯示顯著砷、鎘、銅、錳、鉛及鋅累積於蜆體內，鉻及鎳則無(Mann-Whitney comparison, p<0.05)。 本研究中以不同階層之生物指標，即鱸鰻及亞洲蜆，組成之生物指標組合，並其體內不同部位之金屬累積量，證實了大屯溪存在生物可吸收之金屬污染，並污染對生物造成之衝擊。各檢測金屬中，砷、鎘及鉛對當地生物的潛在影響較大。建議往後針對不同金屬在鱸鰻及亞洲蜆體內之累積機制進行研究，以增進此指標於監測河川金屬污染之實用性。

Many urban rivers have been seriously threatened by metallic pollution for decades due to population growth, industries and economic development. Biomonitoring using representative indicator species has been widely used to assess the pollution impacts in rivers because this approach provides time-integrated results of metal contamination in biota associated with the measurement of the environmental variables to enable a comprehensive understanding of pollution impacts to the river ecosystems. In this study, two bioindicator species including marbled eel (Anguilla marmorata) and Asian clam (Corbicula fluminea) were used in combination to reflect the metallic contamination in a typical urban river, Datun River from the northern Taiwan. Despite seasonal water-quality monitoring of Datun River has been conducted by Environmental Protection Administration (EPA) at an unpolluted site from the upstream section, neither environmental monitoring nor biomonitoring study has been undertaken at the urbanized downstream section with the industrial and residential riparian land-use. In this study, analyses were made for metal concentrations (As, Cd, Cr, Cu, Mn, Ni, Pb, Zn) in different body parts of local-collected A. marmorata and C. fluminea that transplanted at the downstream end of Datun River for 24-days. Metal accumulation level in bioindicators was compared to metal concentration in river water that provided by EPA and measured in this study at the downstream end of Datun River. Results showed that metal pollutants in surface water were concentrated at the downstream end of Datun River comparing to the upstream EPA monitoring site. All study metals were found accumulated in the body of A. marmorata. However, significant difference in concentrations among different body parts was found for As, Cd, Cu, Mn and Zn (Kruskal-Wallis test, p<0.05). The main accumulation site of these metals in eel body included intestine for As (1.20 μg g-1 DW) and Zn (154 μg g-1 DW), liver for Cd (0.66 μg g-1 DW) and Cu (31.9 μg g-1 DW) and vertebrate for Mn (31.1 μg g-1 DW). On the other hand, transplanted C. fluminea showed significant accumulation of As, Cd, Cu, Mn, Pb and Zn while Cr and Ni were not accumulated in their body (Mann-Whitney comparison, p<0.05). We concluded that the use of two bioindicator species from different trophic levels, i.e. A. marmorata and C. fluminea, as combined bioindicators clearly indicated the presence of different bioavailable metallic contaminants and their biological impacts in Datun River based on their bioaccumulation levels in different body parts of A. marmorata and C. fluminea. Among different metals, As, Cd and Pb contaminants showed relatively higher potential to affect local biota. Finally, suggestion was made for further research on metal accumulation mechanisms in A. marmorata and C. fluminea to improve its practical utility on monitoring metallic pollution in river environment.